Heating plate and method for manufacturing it

ABSTRACT

The object of the present invention is a high-performance heating plate and also the method for manufacturing said plate. The heating plate is composed of two basic plate elements, each basic plate being composed, in turn, of a non-electrically-conducting plate on whose surface there is a resistive circuit for the purpose of establishing a surface for dissipation of the energy lost by the passage of the current through the resistive circuit. It is characterized in that, on the basic plate of this invention, use is made of conducting strips supplying power to the resistive surface and configured by means of spraying molten metal. The method that allows production of the plate of this invention makes use of electric-arc metal spraying machines.

OBJECT OF THE INVENTION

The object of the present invention is a high-performance heating plateand also the method for manufacturing said plate.

The heating plate is composed of two basic plate elements, each basicplate being composed, in turn, of a non-electrically-conducting plate onwhose surface there is a resistive circuit for the purpose ofestablishing a region of dissipation of the energy lost by the passageof the current through the resistive circuit.

It is characterized in that, on the basic plate of this invention, useis made of conducting strips supplying electric power to the resistivesurface and configured by means of spraying molten metal.

The method that allows the production of the plate of this inventionmakes use of electric-arc molten metal spraying machines.

The plate of the invention allows the construction of heaters from whichan example will be indicated.

BACKGROUND OF THE INVENTION

There are configurations of heating plates in which use is made of oneor more power supply metal tracks, preferably made of copper, located ona mica plate on which strips of conducting paint are applied.

When it is stated that the paint is conducting it is because it has acertain degree of resistance to the passage of the current such that theproduct of the resistance by the square of the effective intensity isequal to the dissipated power.

The reduction of the section of the conducting paint because the appliedlayer is smaller or because the painted width is smaller gives rise,before the same passage of current, to a higher dissipated power becausethe resistance is increased.

This paint must be applied between two power supply conducting strips sothat the passage of the current occurs through the entire conductingpaint.

It is important for the contact with the power supply tracks to besuitable.

The conducting tracks of the state of the art mainly consist of coppertracks which are adhered on the insulating plate, made of mica, forexample.

A smooth copper tracks gives rise to a poor adherence of the conductingpaint which tends to retract before drying on the metal surface,establishing a poor power supply contact.

This problem has been partly solved in the state of the art by searchingfor varnishes or other substances which are added in a third layer andwhich are useful as an interface between the conducting strip and theconducting paint. Some of these varnishes or substances are mixed withthe same conducting paint to achieve the suitable degree of contactbetween the conducting strip and the conducting paint.

In any case, it is necessary to apply a third strip preventing theproblem of the poor attachment between the conducting track and theconducting paint.

An object of this invention is to establish a manufacturing method whichallows the suitable attachment between the conducting power supply metalstrip and the conducting paint acting as a resistive element.

DESCRIPTION OF THE INVENTION

The essence of the invention consists of a heating plate formed in turnby two basic two plates.

Each of the basic plates is formed by a plate which does not conductelectricity which is useful as a resistant support. The material whichis preferably used is mica or natural stone.

The resistive component which will be used is a conducting paint whichoffers a certain degree of resistance such that the passage of thecurrent through the painted strip dissipates energy in the form of heat,achieving the desired effect: heat generation.

The electric power supply of the strip painted with conducting paint bymeans of two metal tracks between which said conducting paint is placed.These metal tracks polarize and supply power to the conducting paint.

The essence of the invention is in the application of the conductingmetal strips and the attachment with the conducting paint.

The metal strips are sprayed by means of arc molten metal sprayingheads. These spraying heads are usually used for coating surfacesrequiring protection against corrosion, for example.

The heads have a power supply of two metal wires converging at a pointat which they come into contact. Given that the metal wires are suppliedwith electric power, when they come into contact an electric arc isestablished which melts both wires at said point of contact.

The melting occurs continuously because the wires are supplied withpower at a certain speed.

Due to the action of a gas under pressure impinging on the point atwhich the electric arc occurs, the molten metal is sprayed in dropstowards the surface which is opposite the head and in the blowingdirection.

The use, for example, of different metals in each of the metal wiresgives rise to very clean alloys. For its part, the use of suitablychosen spraying gases also establishes a controlled atmosphere.

The molten metal sprayed on the surface of the mica, the materialpreferably used in the embodiments of the invention, is closely attachedto said surface, giving rise to a certain degree of surfaceirregularity, such as waviness.

These surface irregularities of the metal tracks favor the attachmentwith the conducting paint.

The conducting paint is subsequently applied on the plate between thetwo tracks and is partially or completely superimposed on the sprayedmetal tracks.

The roughness of the surface of the metal tracks makes it difficult forthe surface tension effect to remove the paint applied on the metalsurface. Better results are obtained in this application if the paint isalso incorporated by spraying.

The method for obtaining the basic plate is completed by introducingthis plate in an oven at 200 degrees, giving rise to a petrifying phasesuch that all the applied components form a single body.

This plate with the petrified paint can be drilled allowing itsapplication and attachment to other elements with a decorative result,for example.

To prevent the exposure of the parts which are polarized and withpassage of current, two basic plates are superimposed, forming a singleplate with a stratified or sandwich structure.

The sprayed power supply metal tracks extend to a side of the plate forsupplying power from a power supply connector.

The plate thus manufactured and configured is an object of theinvention.

The essential technical features defining it can be expressed byindicating that this plate is formed by the attachment of two basicplates with printed elements for generating heat by resistivedissipation. Each of these basic plates is formed by anon-electrically-conducting plate on which there are defined at leasttwo electric power supply metal tracks incorporated by electric-arcspraying between which there is arranged an area of conducting paint,forming the region of dissipation. It is understood that the indicationthat the track is configured by means of electric-arc spraying is thebest way to establish its configuration on the substrate to which it isincorporated.

This plate can be used to construct an electric power supply heater. Theheater must have the power supply connecting with the terminals of theplate used, and also the protection means so that, if possible, itcannot de directly accessed by the user in order to prevent accidents.

A low-consumption heater making use of two plates such as those of theinvention is especially interesting. A front plate and another innerplate which cannot be accessed due to presence of the former. Aseparation is established between both plates which gives rise to an airchamber favoring natural convection.

The strategy used in the design to favor low consumption consists ofmaking use of two independent thermostats, one for each of the plates,one thermostat regulating the temperature of the rear plate and theother one for the front plate.

The front plate must not reach temperatures greater than 60 or 65degrees centigrade to prevent an accidental contact with the user fromgiving rise to serious burns. The rear plate can reach highertemperatures.

Thus, when the heating is cold and is turned on, the two plates connect,quickly reaching the operating temperature. Once this temperature isreached, given that the rear plate can be placed at higher values, itmaintains the temperature of the front plate by radiation. Thisradiation allows, on one hand, the front plate to remain off most of thetime because its temperature does not decrease and, on the other hand,to achieve the heating by natural convection of the mass of air locatedbetween both plates.

It is possible to incorporate an additional condition for disconnectingthe power supply into this scheme of operation, and such condition isthat the front plate, even disconnected, has a temperature exceeding acertain safety value heated by the rear plate. In this case, the rearplate would also be turned off, reducing even more the consumption andmaintaining the safety of the user. An embodiment of this heater will bedescribed in the section dedicated to the detailed description of theinvention.

DESCRIPTION OF THE DRAWINGS

The present specification is complemented with a set of drawings whichillustrate the preferred example and never limit the invention.

FIG. 1 is a schematic representation of an electric-arc spraying head.

FIG. 2 is an embodiment of a basic plate with which the heating plate isconfigured.

FIG. 3 is a detail of the sectioned basic plate in which the attachmentbetween the conducting paint and the electric power supply metal strip.

FIG. 4 is a schematic embodiment of a heater shown in a plan andelevational view, making use of two plates such as those described inthe previous examples.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an arc spraying head such as the one which will be used inthe method for manufacturing the heating plate of the invention.

This head comprises a pair of metal wires (5) driven by rollers (6) forthe continuous power supply of the head.

Both wires (5) converge at a common point (4). Given that the wires (5)are supplied with power with a potential difference that is sufficientfor an electric arc to be established, both metals melt.

Both wires (5) converge at a common point (4). Given that the wires (5)are supplied with power with a potential difference that is sufficientfor an electric arc to be established, both metals melt.

In this embodiment an aluminium wire (5) and another zinc wire will beused to give rise to an aluminium and zinc alloy. The blowing directionwhich breaks up the molten metal into small drops is indicated by meansof a thick arrow, which drops are sprayed in a cone (7) giving rise tothe adhesion of these drops on the surface (1) on which it impingesuntil forming a metal layer (2).

In this invention the substrate is a mica plate (1) and the metal layer(2) will form the metal track supplying current to the conducting paint(3).

FIG. 2 shows the basic plate which will form the heating plate on whichtwo metal tracks (2) have been sprayed by means of the arc sprayingheads.

These tracks (2) have been configured in an L-shape to achieve thattheir ends reach the edge of the basic plate (1) and can be easilyconnected to a connector (not shown) supplying electric power to theplate (1).

On the metal tracks (2) there is a shaded area showing the region onwhich the conducting paint (3) forming the heat generation area isapplied.

This shaded area corresponding to the conducting paint (3) issuperimposed on part of the area occupied by the metal tracks (2) toachieve the suitable contact between both.

FIG. 3 shows the attachment between the conducting paint (3) and themetal track (2) without the paint completely covering said metal track(2). The interest of this graphic representation is showing the suitable“wetting” of the paint favored by the roughness of the metal projectionpreventing the removal of the paint when it is still not dry.

The paint attempts to cover the area due to the tendency forself-leveling which it has upon covering this area between theelevations forming the metal projections (2).

This configuration of the basic plate is therefore obtained through thefollowing steps:

-   -   Spraying the metal strips (2) by means of the electric-arc head        by melting two metal wires (5).    -   Painting an area between two power supply metal strips (2).    -   Baking the resulting plate for the petrification of the        assembly.    -   Attaching two basic plates thus formed, internally leaving the        printed area to form a heating plate.

Once the plate is formed by the attachment of these basic plates (1),the connectors are incorporated to the prolongations of the metal tracks(2) for the suitable power supply.

The plates thus configured can be drilled and incorporated inside aheating device.

These same boreholes allow incorporating decorative elements or thesupport means for their operational use.

An example of use of this heating plate (1) is shown in FIG. 4. Thisfigure shows an elevational and upper plan view according to a scheme ofdistribution of elements.

The heater constructed making use of the plates (1) has a casing (8)housing two plates (1), a front plate and another rear plate.

The front plate (1) can either be directly accessed by the user or isprotected by a decorative front element (9). In any case, this frontplate (1) is the one closest to the user and is suitable for reachingtemperatures limited by low values such as 60 or 65 degrees centigrade,for example.

In contrast, the rear plate (1) is more protected and it is possible forit to reach higher temperatures. The separation between one plate (1)and the other plate (1) establishes an air chamber which is heated,giving rise to an air current moving by natural convection in an upwarddirection. The heater thus carries out a heating by a dual effect: byradiation and by natural convection.

To achieve the objective that the front plate (1) does not exceed theindicated safety temperature values, it has a thermostat (10)disconnecting the plate (1) once it reaches said temperature.

The rear plate (1) also has a thermostat (11) limiting the operationaltemperature and which will be located above the temperature of the frontplate (1).

Once the front plate (1) reaches the operational temperature, the latterwill be maintained for much more time by the heating by radiation of therear plate (1). It will only be connected again if the cooling by theinner convection current and the heat radiation cools it excessively.Given that for most of the time only one plate (1) is turned on, theconsumption is significantly reduced.

The rear plate (1) will also depend on the thermostat (10) of the frontplate (1) so that if its temperature still very high, it is alsodisconnected.

The location of the wall with respect to the heater is indicated bymeans of a shading located after the casing (5)

Although the thermostats (10, 11) have been located outside the casing(8), their location is only a schematic representation indicating theirpresence, being able to be located at any point giving rise to asuitable reading of the temperature.

1. A heating plate formed by the attachment of two basic plates withprinted elements for generating heat by resistive dissipation, whereineach of these basic plates is formed by a non-electrically-conductingplate (1) on which there are defined at least two power supply metaltracks (2) incorporated by electric-arc spraying between which there isarranged an area of conducting paint (3) forming the region ofdissipation.
 2. The heating plate according to claim 1, wherein thebasic plate makes use of natural stone or mica as anon-electrically-conducting plate.
 3. The heating plate according toclaim 1, wherein the metal tracks (2) are made of an aluminium and zincalloy.
 4. The heating plate according to claim 1, wherein the conductingpaint (3) completely covers the width of the power supply metal track(2).
 5. The heating plate according to claim 1, wherein the conductingpaint (3) partially covers the width of the power supply metal track(2).
 6. The heating plate according to claim 1, wherein the paint (3) ispetrified by baking.
 7. A heater formed by a plate according to claim 1,wherein it is formed by two heating plates (1), a front plate andanother rear plate, leaving an intermediate chamber such that each ofthem has its independent thermostat (10, 11).
 8. The heater according toclaim 7, wherein the thermostat (10) of the front plate (1) is set to atemperature lower than the thermostat (11) of the rear plate such thatthe temperature of the front plate (1) can be maintained by theradiation heat of the rear plate (1).
 9. The heater according to claim8, wherein the thermostat (11) of the rear plate (1) is alsodisconnected when the front plate (1) exceeds a certain predeterminedvalue.
 10. A method for manufacturing a heating plate formed by thefollowing steps: spraying the metal strips (2) by means of anelectric-arc head by the melting of two metal wires (5), painting anarea between the two power supply metal strips (2), baking the resultingplate for the petrification of the assembly, attaching two basic platesthus formed, internally leaving the printed are to form the heatingplate.
 11. The method for manufacturing a heating plate according toclaim 10, wherein the area between the two metal strips (2) by means ofconducting paint (3) is painted by spraying.